PAL-Timing scheme for a normal scan line, no sprites on the current scan line
but at least the sprites 1+2 active on the following scan line:
+---------------------------------------------------------------+
| 1 2 3 4 5 6 |
|123456789012345678901234567890123456789012345678901234567890123|Cycles
+---------[------(--------------------------------------)---]---+Borders
|3-4-5-6-7-rrrrrgggggggggggggggggggggggggggggggggggggggg-N0-1s2s|Phi-1 VIC
| ssss|Phi-2 VIC
|xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxXXX====|Phi-2 CPU
+---------------------------------------------------------------+
'-' = idle bus cycle (reads from the last byte of the video bank)
<num> = pointer fetch for sprite <num> ; g = graphics fetch
s = sprite data fetch ; r = memory refresh cycles
N = extra '-' cycles for NTSC added here
x = processor executes instructions (BA high, AEC high)
X = bus request pending, bus still available (BA low, AEC high);
processor may execute write cycles, stops on the next read cycle.
'=' = bus unavailable (BA low, AEC low); processor is blocked because it
would like to read something.